Gel polymer electrolyte with MXene to extend cycle lifespan of flexible and rechargeable Zinc-Air batteries

Flexible and rechargeable zinc-air batteries (ZABs) are promising energy sources for wearable electronic devices due to their high energy density and safe operation. However, the performance of quasi-solid-state electrolytes gradually degrades during the ion-exchange process, mainly because of water evaporation on the open cathode side, which reduces the lifespan of ZABs. Thus, a novel electrolyte needs to be designed that can retain water to increase the cycle lifespan of ZABs. Herein, we propose a near-neutral gel polymer electrolyte (GPE) composite comprising polyvinyl alcohol (PVA) and hydroxy-functionalized MXene. Benefiting from the three-dimensional porous network and numerous surface-functionalized hydroxy groups, the network of alkalized MXene inside the PVA matrix serves as a water reservoir, resulting in enhanced water retention, and therefore, a high ionic conductivity of 77.6 mS cm(-1). The molecular dynamic simulations validate stronger hydrophilicity of alkalized MXene surface for water molecular than the pristine MXene. Resultantly, the assembled ZABs show a long cycle lifespan of 160 h at a current density of 2 mA cm(-2) and a charging-discharging period of 15 min.